1. Field of the Invention
The present invention relates to a printing element substrate, a printhead, and a printing apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2009-29117 describes an inkjet printing apparatus represented by a printer or the like. The inkjet printing apparatus includes a printhead for executing printing on a printing medium. The printhead includes a printing element substrate. The printing element substrate includes a printing unit for executing printing, a processing unit for processing print data, a level shifter for performing the level shift of an active signal from the processing unit, and outputting the signal to the printing unit, and a voltage generation unit for generating a voltage to be used by the level shifter to perform a level shift. The printing unit includes a printing element and a driving transistor for driving the printing element.
A plurality of different power supply voltages are supplied to the printing element substrate. The processing unit uses a power supply voltage for a logic circuit. The printing unit uses a power supply voltage for driving the printing element. Furthermore, the voltage generation unit uses a power supply voltage for generating a voltage to be supplied to the level shifter.
When the order of supply of the plurality of power supply voltages is wrong or the printhead is not appropriately mounted, only some of the plurality of power supply voltages may be supplied. For example, not the power supply voltage for the logic circuit but other power supply voltages may be supplied. In this case, since the potential of the power supply node of the logic circuit is indefinite, this may cause, for example, an operation error of the printing unit. Furthermore, a current (for example, a through current) generated when the potential of the power supply node of the logic circuit is indefinite may increase the power consumption.
Note that Japanese Patent Laid-Open No. 2009-29117 discloses an arrangement in which when no power supply voltage for the logic circuit is supplied to the printing apparatus, the drive transistor for receiving a signal from the level shifter is rendered non-conductive by prohibiting supply of a voltage to the level shifter, thereby preventing an operation error of the printing unit. The arrangement described in Japanese Patent Laid-Open No. 2009-29117, however, does not consider the current of the voltage generation unit for generating a voltage to be supplied to the level shifter.